Various fastening systems have been devised to mount electronic components to circuit boards. In one example, the mounts include threaded studs which are soldered directly to the circuit board after being inserted into holes in the board. Other systems include the use of a broaching-type fastener in which the shank of the fastener includes longitudinal splines, which pierce and wedge into the sidewalls of pre-drilled holes in the board to secure the fastener to the board. Both studs having external male threads and nuts with threaded bores have been used in the past as circuit board mounting devices. Rivet-type fasteners with a fluted shank flared over the back side of the circuit board have been tried but are not commonly employed because the flared-over end of the fastener may present an obstruction to components or circuits on the opposite side of the board.
The soldered-in type fasteners require that the fasteners be placed on the board either before board soldering or require an additional soldering step after the fastener is inserted into the board. Broaching-type fasteners place unwanted high insertion pressures on the board when they are pressed in. This often causes the board to crack and the need for placing attachment holes away from the edge of the board. Therefore, their use is restricted to thicker circuit boards and placement a safe distance from the edge of the board. Furthermore, they cannot be used with boards which are made of brittle materials.
Another problem with broaching-type fasteners occurs when they are used with plated through-holes. The fastener mounting hole is often plated with a thin coating of electrically conductive material to form an electrical connection between opposite sides of the board. When a broaching-type fastener is used in a plated through-hole, the splines on the shank of the fastener which cut into the board often cut away much of the plating on the inner walls of the through-hole. This adversely affects the quality of the electrically-conductive properties of the through-hole plating.
The closest prior art of which the applicant is aware are U.S. Pat. No. 4,110,904, entitled "Substrate with Terminal Connections and Method of Making the Same", issued to Samuel B. Johnson on Sept. 5, 1978; U.S. Pat. No. 4,911,592, entitled "Method of Installation and Installation Apparatus", issued to Rudolph R.M. Muller on Mar. 27, 1990; and, U.S. Pat. No. 3,659,245, entitled "Variable Resistor Pin Terminal and Method", issued to Robert L. Payne on Apr. 25, 1972. These prior art references are pertinent in that they show fasteners and fastening methods similar to the present invention, however, neither reference teaches or suggests its novel and unobvious features of the present invention.
There is, therefore, a need for a simple, press-in type circuit board fastener which can be used with thin circuit boards of any material, and which will not adversely affect the electrical properties of plated through-holes into which they are inserted. There is a further need for a circuit board fastener which may be inserted by a pressing force, but which does not overly stress the circuit board so that it may be used with relatively thin board and located close to the edge. It is the object of the present invention to provide a circuit board fastener which fulfills these and other unsatisfied needs in the circuit board arts.